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| Mulberries, one of the berries reported to have cancer preventing nutrients. © by Ruth Zachary |
The following information was slightly abridged
from an article By Tom Philpott, food and ag. correspondent for Mother Jones (July
23, 2014) The article was sent by a friend of mine, about the complex chemistry
of plants, and how it works within the human body, is relevant to much that is included on
this blog, and I thought it might be interesting to people who follow my health
information. I like the fact that
several contributors were credited with parts of the general challenge to
conventional beliefs about plant and human biochemistry, including possible ill
effects from supplements. Readers may want to pursue the topic further on their own.
“Plants
can't move. They're sitting targets for every insect, two- and four-legged
creature, and air-borne fungus and bacteria that swirls around them. But
they're not defenseless.... Under pressure from millions of years of attacks,
they've evolved to produce compounds that repel these predators. Known as
phyotochemicals, these substances can be quite toxic to humans.
“But
other phytochemicals have emerged as crucial elements of a healthful human
diet. Indeed, they're the source of several essential vitamins, including A, C,
and E. But according to a Nautilus article by
the excellent science journalist Moises Velasquez-Manoff (author of a recent Mother
Jones piece on the gut microbiome),
our view of how these defensive compounds benefit us might be wildly wrong.
“The accepted dietary dogma goes like this: The
phytochemicals we ingest from plants act as antioxidants—that is, they protect
us from the oxidative molecules, known as "free radicals," that our
own cells produce as a waste product, and that have become associated with a
range of degenerative diseases including cancer and heart trouble.
“Many phytochemicals and the vitamins they carry have been
proven in lab settings to have antioxidant properties—that is, they prevent
oxidization. And so, Velasquez-Manoff shows, the idea gained currency that
fruits and vegetables are good for us because their high antioxidant load
protects us from free radicals. And from there, it was easy to leap to the
conclusion that you could slow aging and stave off disease by isolating certain
phytochemicals and ingesting them in pill form—everything
from multivitamins to trendy antioxidants like resveratrol. "A supplement
industry now worth $23 billion yearly in the U.S. took root," he notes.
“And yet, antioxidant pills have proven
to be a bust. In February, a group
of independent US medical researchers assessed
10 years of supplement research and found that pills loaded with vitamin E and
beta-carotene (the stuff that gives color to carrots and other orange
vegetables) pills are at best
useless and at worst harmful—that is, they may trigger lung
cancer in some people. Just this month, a meta-analysis published
in the New England Journal of Medicine found that antioxidant supplements
"do not prevent cancer and may accelerate it."
“And a 2009
study found that taking antioxidant supplements
before exercise actually negates most of the well-documented
benefits of physical exertion: That is, taking an antioxidant pill before a run
is little better than doing neither and just sitting on the couch.
“So what gives? Velasquez-Manoff points to emerging
science suggesting that phytochemicals' antioxidant properties may have thrown
us off the trail of what really makes them good for us. He offers two key
clues. The first is that plants produce them in response to stress—e.g.,
pathogenic bacteria, hungry insects. The second is that exercise itself is a
form of self-imposed stress: You punish your body by exerting it, and it
responds by getting stronger. Leaning on the work of Mark Mattson, Chief
of the Laboratory of Neurosciences at the National Institute on Aging, and
other researchers, Velasquez-Manoff proposes that phytochemicals help us not by
repelling oxidant stresses, but by triggering them.
“Consider that exercise actually generates free
radicals in our muscles—the very thing, according to current dogma, that makes
us vulnerable to cancer and aging. But a while after a bout at the gym or on
the running trail, these free radicals disappear, replaced by what
Velasquez-Manoff calls "native antioxidants." That's because, he
writes, "post-exercise, the muscle cells respond to the oxidative stress
by boosting production of native antioxidants." And these home-grown
chemicals, "amped up to protect against the oxidant threat of yesterday’s
exercise, now also protect against other ambient oxidant dangers" like
ones from air pollution and other environmental stressors, he writes. In
the exercise study, the supplements may have interrupted the process, the
study's main author, Swiss researcher Michael Ristow, tells
Velasquez-Manoff—they prevent the body from producing its antioxidants, but
what they deliver doesn't offset the loss.
“Yet phytochemicals found in whole foods—"the hot
flavors in spices, the mouth-puckering tannins in wines, or the stink of
Brussels sprouts"—may work on our bodies much as exercise does.
Velasquez-Manoff writes: "Our bodies recognize them as slightly toxic, and
we respond with an ancient detoxification process aimed at breaking them down
and flushing them out." “
"To bolster his case, Velasquez-Manoff cites the example of
sulforaphane, the compound that gives broccoli and other members of the brassica family
of vegetables—such as Brussels sprouts—their sulfurous smell when they cook.
It's what's known as an "antifeedant"—i.e., it's pungency discourages
grazing (and makes many people hate Brussels sprouts, etc). Unlike many
phytochemicals, sulforaphane isn't an antioxidant at all, but rather a mild
oxidant—that is, it mimics free radicals and thus under the old dietary dogma,
we should avoid it. And yet...
"When sulforaphane enters your blood stream, it triggers
release in your cells of a protein called Nrf2. This protein, called by some
the “master regulator” of aging, then activates over 200 genes. They include
genes that produce antioxidants, enzymes to metabolize toxins, proteins to
flush out heavy metals, and factors that enhance tumor suppression, among other
important health-promoting functions. In theory, after encountering this humble
antifeedant in your dinner, your body ends up better prepared for encounters
with toxins, pro-oxidants from both outside and within your body, immune
insults, and other challenges that might otherwise cause harm.
"In this theory, what causes cancer and general aging isn't
oxidative stress itself, but rather a poor response to oxidative stress—"a
creeping inability to produce native antioxidants when needed, and a lack of
cellular conditioning generally." And that's where the modern Western
lifestyle, marked by highly processed food and a lack of physical exertion,
comes in.
"[The National Institute on Aging's] Mattson calls this the
"couch potato" problem. Absent regular hormetic stresses, including
exercise and stimulation by plant antifeedants, “cells become complacent,” he
says. “Their intrinsic defenses are down-regulated.” Metabolism works less
efficiently. Insulin resistance sets in. We become less able to manage
pro-oxidant threats. Nothing works as well as it could. And this mounting
dysfunction increases the risk for a degenerative disease.
"While this emerging view of phytochemcials is compelling, Velasquez-Manoff
acknowledges that it isn't fully settled. For one thing, it's unclear why
isolated phytochemicals in pills don't seem to work the same magic as they do
in the form of whole foods.
Here's Velasquez-Manoff:
"Proper dosage may be one problem, and interaction between
the isolates used and particular gene variants in test subjects another.
Interventions usually test one molecule, but fresh fruits and vegetables
present numerous compounds at once. We may benefit most from these simultaneous
exposures. The science on the intestinal microbiota promises to further
complicate the picture; our native microbes ferment phytonutrients, perhaps
supplying some of the benefit of their consumption. All of which highlights the
truism that Nature is hard to get in a pill.
"But human nutrition is a deeply interesting topic
precisely because it resists being settled. As Michael Pollan showed in his
2008 book In Defense of Food, humans have adapted to a wide
variety of diets—from the Mediterranean and Mesoamerican ones based mostly on
plants, to the Inuit ones focusing heavily on fish. The one diet that hasn't
worked very well is the most calibrated, supplemented, and
"fortified" of all: the Western one."
